Fracture Mechanics Approach to Fatigue Crack Propagation

So far it has been analyzed the phenomenology that precedes the macro-crack formation and studied all those factors, both mechanical and metallurgical, that have a role in the macro-crack formation that closes Stage I of fatigue (see Sect.  2.7 and Fig.  2.47 ). The next phase, Stage II, is that in which the macro-crack is directly opened by stresses normal to the crack plane and grows at each applied cycle.